The embodiments disclosed relate generally to gas and liquid fuel turbines, including both can-annular or annular combustion systems, and methods of operating such combustion systems.
Dry Low NOx technology is routinely applied for emissions control with gaseous fuel combustion in industrial gas turbines with can-annular combustion systems through utilization of premixing of fuel and air. The primary benefit of premixing is to provide a uniform rate of combustion resulting in relatively constant reaction zone temperatures. Through careful air management, these temperatures can be optimized to produce very low emissions of oxides of nitrogen (NOx), carbon monoxide (CO) and unburned hydrocarbons (UHC). Modulation of a center premix fuel nozzle can expand the range of operation by allowing the fuel-air ratio and corresponding reaction rates of the outer nozzles to remain relatively constant while varying the fuel input into the turbine.
Fuel staging is well-understood by those experienced in the art as a means of achieving higher turbine inlet temperatures with uniform heat release. Axially staged systems employ multiple planes of fuel injection along the combustor flow path. Utilization of axial fuel staging requires special design considerations to inject fuel into the high temperature products of combustion. The high temperature and pressure environment of the latter stages of an axially staged combustor have prevented development of robust designs suitable for commercial applications.
It would therefore be desirable to develop new gas turbines having a fuel system configuration and/or utilizes a method of staging fuel so that lower peak fuel temperatures are achieved. Such gas turbines would be expected to have correspondingly low NOx and CO emissions. The ability of a new gas turbine to exhibit of an increased range of operability within such “Emissions Compliant” regimes would provide further advantages.